Apply path generation for superclasses to Load._set_path_strategy()

Extended the fix first made as part of :ticket:`3287`, where a loader option
made against a subclass using a wildcard would extend itself to include
application of the wildcard to attributes on the super classes as well, to a
"bound" loader option as well, e.g. in an expression like
``Load(SomeSubClass).load_only('foo')``.  Columns that are part of the
parent class of ``SomeSubClass`` will also be excluded in the same way as if
the unbound option ``load_only('foo')`` were used.

Fixes: #4373
Change-Id: I2eee0e587c34323a77df077b9cb699da370c403d

1 files changed, 9 insertions, 3 deletions

diff --git a/lib/sqlalchemy/orm/strategy_options.py b/lib/sqlalchemy/orm/strategy_options.py
index af9bd71b6..0ef34b0b9 100644
--- a/lib/sqlalchemy/orm/strategy_options.py
+++ b/lib/sqlalchemy/orm/strategy_options.py
@@ -357,9 +357,15 @@ class Load(Generative, MapperOption):
         else:
             effective_path = self.path
 
-        self._set_for_path(
-            self.context, effective_path, replace=True,
-            merge_opts=self.is_opts_only)
+        if effective_path.is_token:
+            for path in effective_path.generate_for_superclasses():
+                self._set_for_path(
+                    self.context, path, replace=True,
+                    merge_opts=self.is_opts_only)
+        else:
+            self._set_for_path(
+                self.context, effective_path, replace=True,
+                merge_opts=self.is_opts_only)
 
     def __getstate__(self):
         d = self.__dict__.copy()